1. Field of the Invention
The present invention relates to an IC (Integrated Circuit) package, and in particular to a PCB (Printed Circuit Board) reinforcement structure for preventing the deformation of and damage to a thin printed circuit board (for example, a printed circuit board having a thickness of not more than 0.4 mm), and an integrated circuit package using the same.
2. Description of the Related Art
Recently, due to the miniaturization, thinning, and weight reduction of electronic appliances, highly integrated circuit packages are required. For this reason, the super-thin design of printed circuit boards is also required.
A printed circuit board serves to mechanically fix electronic parts mounted thereon, beyond electrically interconnecting the electronic parts. Therefore, such a printed circuit board should maintain mechanical strength to such an extent that it is not deformed or damaged during a fabrication process of electronic appliances or a packaging process of the printed circuit board.
In general, however, if the thickness of a printed circuit board is reduced, the rigidity (mechanical strength) of the printed circuit board is also reduced, whereby the printed circuit board is subjected to deformation, such as flexure, distortion, etc., and its reliability is deteriorated. Therefore, the practical lower limit for printed circuit board thickness has been limited to about 1.0 mm up to now.
The conventional method for overcoming the limitation in thickness of a printed circuit board is to reinforce a printed circuit board material with filler, such as glass fiber, so as to increase the rigidity of the printed circuit board. However, this conventional method induces a quality problem, such as the deterioration of molding workability, and a difficult recycling problem due to the use of a material harmful for human body and environment.
There is another conventional method for increasing the strength of the printed circuit board by introducing resin between a printed circuit board, on which a SMD (Surface Mounting Device) process is completed, and a mold, and then curing the resin. However, according to this method, the processes for making the mold come into close contact with the printed circuit board, and introducing the resin are very complicated. In addition, since resin residue remains in a gap between the printed circuit board and the mold, a post process for smoothing the surfaces of the printed circuit board is required. Consequently, this method is not suitable for mass production. Specifically, there is a disadvantage in that the resin contracts while it is being cured, thereby rendering the printed circuit board warped.
Another conventional method for increasing the strength of a printed circuit board is to spray resin on a printed circuit board, on which a surface mounting device processing is completed, and then curing the resin. However, the length of time required for spraying the resin is long. In addition, it is necessary to separately block one or more areas, to which the resin shall not be applied. Consequently, this method is also not suitable for mass production.